Unfortunately this is not the 1960 or 70's. Back then you could look at pretty much any car with this problem and quickly determine if the problem was on the ignition side or the fuel delivery side. And if on the ignition side it was almost always the points, and you could very quickly re-gap them or replace them if needed.

Modern cars however have very complex computerized engine management systems. So now, if any one of a dozen sensors is giving faulty data or no data to the ECU it might keep your car from starting. On the plus side however the cars brain also diagnoses most problems for you. So anytime you have an engine problem with a modern car the first thing you do is see if the engine check light is on and if so you hook up a code reader and get all the current error codes, if any. The problem could be anything from a crank angle sensor (well, not on your car) to MAF sensor and there is no point guessing until you check for codes. Your car is pre ODB2 of course but if you use a wire to connect the A and B terminals on the test port you should be able to get the ECU to flash out the codes for you (long and short dashes). Then just look them up online.

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Do you have spark? If not than I would suspect a bad crank sensor. If you do than you could possible have a bad PCM or check for power to the injectors. You could have a blown fuse for the injectors which are controlled on the ground side by the PCM.

check for spark if there is no fuel coming out of injectors you can borrow noid lights from orielies auto parts check the injectors for pulse width if you have no pulse your computer is bad if vyou have no spark remove dist ributer cap and see if rotor turns while cranking if it does check for spark between coil and dist if no spark you more then likely have a bad ignition module

If the check engine light never comes on, on the dash, with the ignition turned on, then the jeep will not start. You should try hooking up a noid light to the fuel injector wires, to see if the ecu is pulsing the injector while cranking. If the ecu does not send a pulse then the crank sensor or the ecu itself is bad and needs repair.

Does the check engine light on your dash light up when you turn on the ignition, before trying to crank the engine? Does the fuel pump come on for a second, and prime the fuel lines, when you turn the ignition on? Does the fuel injector wires get the pulse signal from the ecu while cranking? If not, your jeep ecu might be in need of repair. It's a common problem with that generation of grand Cherokees.

my first thought based on what I could see in your description (you cannot see the entire post until you click on it) was the ECU-you have done a check of the fuel pressure, and checked the regulator for leaks, correct? I would try a junkyard ECU (25 to 50 dollars in most places) or on ebay. Also carefully examine the crank sensor connector, and the harness itself for damage-no crank sensor signal, no pulse. ECU's do not normally go bad, but it does happen.

No injector pulse at injectors: a) check fuses b) use scan tool to read RPM at PCM while cranking. Ask question specifying RPM PID data. c) crank sensor/cam sensor/ign. module/wiring fault d) stuff not plugged in properly 4) check fuses 5) dead PCM note PCM pulses injector ground based on sensor input, power is constant from ignitionhow are you testing injectors theres something called a noid light auto parts store let you use them free you have to test it on the injector itself what did you car do before it died does it turn over but not start

The computer is the ground for the injectors. Recheck the harness with some one cranking the engine. if the meter doesn't fluctuate the the drivers are bad in the computer. you have to replace the computer

Replace ignition module. Engine computer is related only to the fuel injectors. Spark is only controlled by ignition module. Make sure that you replaced the prom chip inside the computer when you did your switch as well.

For the fuel injectors to pulse (open and deliver fuel to the engine) they need a command from the computer. The computer gets information/signal to operate the injectors from the ignition module. The ignition module receives its information from the crank and camshaft position sensors. For the computer to pulse the injectors yet the engine is not running indicates there is an erratic signal being created. About the only way this can happen is if there is a bad ground wire. The computer, ignition module and sensors rely on a good power supply to operate. But more importantly these systems require a good electrical ground. There are several ground wires that are dedicated to these components. Failure of just one of these wires can send the system into total chaos. The result is a confusing condition much like you’re describing. Prove the condition of the grounds and you’ll likely be up and running again.